updated 'README.md'
Updated main files

- Changed class/id names for expandable and hidden elements
- Started adding an 'About' section in 'index.html'
- Updated 'main.js' so that when an expand-arrow is clicked, the page
scrolls to the appropriate section.
Updated 'style.css','index.html','main.js'

- Moved contact info into it's own expandable section
- Updated the "Change Map Size" button so that its function makes the
map even bigger than before.
Updated 'style.css'

- Changed `body` height, added rules for headers. This makes the default
map bigger.
Updated all main files
Updated 'main.js' so that "Change Map Size" button works properly.
Merge branch 'release_1.3' into develop